Hemodialysis machines commonly monitor pressure in an extracorporeal blood circuit, for example, pressure from a blood chamber containing a blood-air interface. An air-filled tube connects the blood chamber to a pressure port of the machine. A transducer protector, containing a hydrophobic membrane, is positioned between the blood chamber and the pressure port. The membrane provides a sterile barrier to the blood circuit and prevents blood contamination of the machine, yet allows air pressure to pass through the membrane and act on the pressure transducer inside the machine. Problems with such a blood-air interface system include clotting, heparin dosage concerns, contamination, and inaccurate pressure measurements. Air contact with blood results in clotting that can collect in portions of the blood circuit, reducing treatment effectiveness. Clotting can also occasionally require replacement of the dialyzer during treatment. To reduce clotting during dialysis, a patient is typically administered a dosage of heparin, sufficient to allow adequate treatment time, yet allow the patient's clotting factor to return to normal levels prior to termination of the treatment. The use of heparin adds cost to the treatment and increases the potential for hazardous blood loss. The hydrophobic membrane in the transducer protector is very thin, and occasionally allows blood contamination of the pressure monitoring circuit on the dialysis machine. When this occurs, the contaminated portion of the machine must be cleaned and sanitized before the machine can be used again. Occasionally, during dialysis, abrupt pressure changes in the blood circuit, or air leaks in the pressure port connection, allow the blood level to reach the hydrophobic membrane in the transducer protector. Blood contact with the membrane occludes air channels through the membrane, which can inhibit or prevent pressure transfer to the transducer of the dialysis machine. This condition can reduce the response time of the machine, to pressure changes, or can prevent pressure monitoring completely.